Background: Gastrointestinal cancers (colorectal cancer, gastric cancer and esophageal cancer) are the most prevalent malignant tumors in China, resulting in 975,537 new cases and 958,675 deaths in 2020. Currently, the gold standard for the early detection of these cancers remains to be gastrointestinal endoscopy. However, the invasiveness, low throughput and high cost of these procedures have prevented its wide acceptance by Chinese population. The objective of this study was to develop a liquid biopsy test based on the detection of multiple DNA methylation biomarkers (SpecGastro test) and evaluate its clinical performance for early detection of gastrointestinal cancers. Methods: Two hundred and eighty-two gastrointestinal cancer patients (98 colorectal cancers, 136 gastric cancers and 48 esophageal cancers) and 195 control subjects were included. Ten milliliters of peripheral blood was drawn and 3.5 mL plasma was separated for cell-free DNA extraction and bisulfite conversion. The converted DNA was subsequently examined by SpecGastro test, a multiplex qPCR assay that detected six methylation biomarkers and one internal control. Results: Overall sensitivity for SpecGastro test was 76.6% (95% CI: 71.1-81.3%) with a specificity of 89.2% (95% CI: 83.8-93.1%). Sensitivities for colorectal cancer, gastric cancer and esophageal cancer were 87.8% (95% CI: 79.2-93.2%), 69.9% (95% CI: 61.3-77.3%) and 72.9% (95% CI: 57.9-84.3%), respectively. A high AUC of 0.903 (95% CI: 0.873-0.928) indicated that SpecGastro test distinguished gastrointestinal cancer patients from control subjects with high accuracy. Conclusions: Our analysis demonstrated the utility of SpecGastro test to detect three types of gastrointestinal cancers with high sensitivity and specificity. These results supported the feasibility of this blood-based SpecGastro test as a complementary tool to the existing single-cancer early detection tests.